Corona discharge occurs when a sufficient voltage is applied between two conductors with an appropriate geometry to ionize a fluid, such as air, between the conductors, causing ions to flow from one of the conductors to the other. Additionally, the ions may interact with other particles in the fluid. Corona discharge has been previously used in early-generation desktop laser printers and is still used in high-speed laser-based presses and printers to apply electrostatic charge to an imaging drum.